DESCRIPTION: (Applicant's Abstract) Amphetamine (AMPH) elicits a species-specific pattern of motor activation that, in animals, has been shown to be mediated at least in part by the striatum. If the neuronal patters established in the striatum are critically involved in shaping the motor response to AMPH, as ample data suggest, then some aspect of these patterns should be communicated to its primary efferent structure the substantial nigra pars reticulate (SNr). Research in this application seeks to further understanding of the nigral mechanisms of AMPH-induced motor response in two ways. The first is to investigate the role of the SNr in the normal motor response of rats walking on a treadmill or performing a conditioned-reinforcement task. After surgery to implant microwire bundles for recording of single units in the SNr, rats will be placed in a chamber with a treadmill or one with two nose-poke holes and a spout for liquid sucrose delivery located on one wall. Single-unit activity will be monitored throughout performance of these tasks, which should yield numerous instances of head movements, oral behavior (e.g., licking) and locomotion. The second aim of the research proposed here is to correlate AMPH-induce changes in SNr activity and behavior the pre-drug behavioral response of the neuron. After performing the behavioral tasks, rats will be placed in an open-field environment where unit activity will be monitored after subcutaneous infections of either AMPH (1.0 or 5.0 mg/kg) or saline. These experiments will provide valuable information about the way in which the SNr influences motor- related target structures and how AMPH changes this output to produce its characteristic pattern of repetitive or stereotype movement.